Use the trigonometric subtraction formula for sine to verify this identity:

cos((π / 2) – x) = sin x

answer format:

calculation:

1.

2.

reason:

1. -this follows from the difference formula for cosine

2. -this follows by evaluating at π / 2

this proves the identity:

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Adam is building a deck in his backyard around a tree. the deck is in the shape of a regular octagon. in the center of the deck, there is a hole for the tree. if a = 10.9 ft, s = 9 ft, and the diameter of the hole is equal to 7 ft, find the area of the deck to the nearest tenth of a square foot. (use 3.14 as an approximation of pi.)